1. Field of the Invention
The present invention relates to a thermal printer and a portable terminal.
2. Description of the Related Art
Hitherto, a thermal printer has been known as a printer configured to perform printing on a recording sheet (heat-sensitive paper). The thermal printer includes a thermal head, a platen roller, and a frame. The thermal head includes a heating element. The platen roller is configured to feed the recording paper by nipping the recording paper with the thermal head. The frame includes a shaft support portion which is configured to support the platen roller so that the platen roller is rotatable about an axis thereof. In the thermal printer, the heating element of the thermal head is caused to generate heat as appropriate during a course of feeding the recording paper through rotation of the platen roller, thereby being capable of printing various information on the recording paper.
The above-mentioned platen roller is rotated by transmission of power of a motor through intermediation of a speed reduction mechanism. The motor is arranged on an inner side of the frame in an axial direction with respect to the shaft support portion. Further, the speed reduction mechanism is arranged on an outer side of the frame in the axial direction with respect to the shaft support portion. The speed reduction mechanism includes a two-step gear, specifically, a gear which includes a large gear and a small gear having different numbers of teeth and being arrayed in the axial direction. The speed reduction mechanism is covered with a gear cover from the outer side in the axial direction.
Incidentally, particularly for a thermal printer which is to be mounted to a portable terminal such as a card payment terminal, downsizing in the axial direction, that is, in a width direction of recording paper has been demanded. The dimension of the thermal printer in the axial direction is determined based on the thicknesses of the shaft support portion, the speed reduction mechanism, and the gear cover, in addition to a width of recording paper to be used.
However, in the above-mentioned related-art thermal printer, there is difficulty in reduction of the thicknesses of the shaft support portion, the speed reduction mechanism, and the gear cover in consideration of durability, and hence there has been a limit in the downsizing in the axial direction. Therefore, the downsizing in the axial direction has been demanded for the thermal printer of this type.